The present invention relates to pigment-comprising aqueous formulations which comprise at least one aqueous addition-polymer dispersion.
Pigmented formulations are employed widely in the form of coating compositions, especially emulsion paints, synthetic-resin-bound plasters (dispersion plasters), sealing compounds or filling compositions for purposes of architectural protection or decoration. Pigmented formulations generally include as their binder a film-forming polymer, at least one inorganic pigment and, if desired, one or more inorganic fillers/extenders, and customary auxiliaries. The quality of the coatings formed from pigmented formulations depends critically on the ability of the film-forming polymer to carry out uniform binding of the nonfilm-forming constituents, the pigments and the inorganic fillers.
A low pigment binding capacity leads to poor mechanical stability of the coating, which is manifested, for example, in a low wet abrasion resistance. The desire, however, is for high wet abrasion resistance, especially in the case of washable emulsion paints.
The pigment binding capacity of the binder plays a particularly important part in formulations having a moderate to high content of inorganic pigments and fillers/extenders. A characteristic parameter of the pigment content of a polymer-bound coating composition is the pigment volume concentration pvc. The pvc is usually defined as the percentage quotient of the overall volume of solid inorganic constituents (pigment+fillers/extenders) divided by the overall volume of the solid inorganic constituents and of the polymer particles of the aqueous binder polymer dispersion; see Ullmanns Enzyklopxc3xa4die der technischen Chemie, 4th edition, volume 15, p. 668.
In the case of exterior applications in particular, the coating compositions should be stable to environmental influences such as sunlight, moisture and fluctuations in temperature. In addition, the coating composition must adhere well to a variety of substrates even when exposed to moisture, which again depends on the chosen binder polymer.
Another property dependent on the binder polymer is the blocking resistance of the coatings.
WO 93/11181 discloses titanium dioxide-containing formulations comprising, as dispersing auxiliaries, aqueous addition-polymer dispersions whose polymers include itaconic acid copolymerized in an amount of more than 1% by weight based on the weight of the addition polymer. The wet abrasion resistance of the dispersions disclosed therein leaves much to be desired.
EP-A-810 274 discloses binders for solvent-free coating compositions which may comprise acid-functional monomers copolymerized in an amount of up to 1% by weight based on the overall weight of the monomers to be polymerized.
The prior art binders are able to go only some of the way toward meeting the requirements that are placed on coating compositions.
It is an object of the present invention to provide pigmented formulations having a high pigment binding capacity and, therefore, high wet abrasion resistance. These properties must be ensured even at relatively high pigment volume concentrations, i.e., at pvc  greater than 40%. The formulations should also be stable on storagexe2x80x94that is, their viscosity should show little or no increase even on prolonged storage.
We have found that this object is achieved by using for the formulations binders based on aqueous addition-polymer dispersions whose polymers comprise from 0.1 to 1.5% by weight of itaconic acid in copolymerized form.
The present invention accordingly provides pigment-comprising aqueous formulations comprising
i) at least one copolymer P of ethylenically unsaturated monomers M in the form of an aqueous polymer dispersion which comprises from 0.1 to 1.5% by weight, based on the overall weight of the copolymer P, of itaconic acid as acidic monomer M1, its salts and/or its anhydride in copolymerized form, it being possible for up to 50% by weight of the itaconic acid to be replaced by another monomer having at least one acid group or one neutralized acid group, and has a glass transition temperature TG in the range from xe2x88x9210 to +50xc2x0 C.,
ii) at least one inorganic pigment,
iii) if desired, inorganic fillers/extenders, and
iv) customary auxiliaries.
The monomers M of which the copolymer P is constructed preferably make up from 0.2 to 1.2% by weight, in particular from 0.2 to 1.0% by weight and, with particular preference, from 0.4 to 1.0% by weight. In an especially preferred embodiment the monomers M comprise from 0.5 to 0.9 and, specifically, from 0.5 to 0.8% by weight of itaconic acid as acidic monomer M1. Instead of itaconic acid it is also possible to employ its anhydride or its salts to prepare the copolymers P. A certain fraction of the itaconic acid, namely up to 50% by weight, but preferably not more than 25% by weight and in particular not more than 10% by weight, can be replaced by another monomer having at least one acid group; for example, by an ethylenically unsaturated carboxylic acid, such as acrylic acid or methacrylic acid, or by an ethylenically unsaturated sulfonic acid, an example being vinylsulfonic acid or its salts. Typical salts are the alkali metal and ammonium salts, preferably the sodium salts. Particular preference is given to employing itaconic acid as the sole acidic monomer (monomer M1).
Normally, the preparation of the copolymers P comprising itaconic acid takes place by free-radical addition polymerization of ethylenically unsaturated monomers M which in addition to itaconic acid include at least one further comonomer. Suitable comonomers are generally selected from vinylaromatic monomers, such as styrene, xcex1-methylstyrene, o-chlorostyrene or vinyl-toluenes, the vinyl esters of aliphatic C1-C18 monocarboxylic acids, such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl hexanoate, vinyl 2-ethylhexanoate, vinyl decanoate, vinyl pivalate, vinyl laurate, vinyl stearate, and commercial monomers VEOVA(copyright) 5-11 (VEOVA(copyright) X is a tradename of Shell and stands for vinyl esters of xcex1-branched, aliphatic carboxylic acids having X carbon atoms, which are also referred to as versatic(copyright) X acids), and the esters of ethylenically unsaturated C3-C8 mono- or dicarboxylic acids with C1-C18-, preferably C1-C12-and, in particular, C1-C8-alkanols or C5-C8-cycloalkanols. Examples of suitable C1-C18-alkanols are methanol, ethanol, n-propanol, i-propanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, n-hexanol, 2-ethylhexanol, lauryl alcohol and stearyl alcohol. Examples of suitable cyclolkanols are cyclopentanol and cyclohexanol. Particularly suitable esters are those of acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid or fumaric acid. The esters concerned are especially those of acrylic and/or methacrylic acid, such as methyl, ethyl, isopropyl, n-butyl, isobutyl, 1-hexyl, tert-butyl and 2-ethylhexyl (meth)acrylates, and also the esters of fumaric and maleic acid, examples being dimethyl fumarate, dimethyl maleate and di-n-butyl maleate. Also suitable are nitriles of xcex1,xcex2-monoethylenically unsaturated C3-C8 carboxylic acids, such as acrylonitrile or methacrylonitrile. It is also possible, furthermore, to employ C4-C8 conjugated dienes, such as 1,3-butadiene, isoprene or chloroprene xcex1-olefins, such as ethylene, propene and isobutene, and vinyl chloride or vinylidene chloride as comonomers.
In addition to itaconic acid the monomers M preferably include from 50 to 99.9% by weight, based on the overall weight of the copolymer P, of at least one monomer M2 selected from the abovementioned vinylaromatic monomers, the abovementioned esters of ethylenically unsaturated C3-C8 monocarboxylic acids with C1-C12-alkanols, and the vinyl esters of aliphatic C1-C12 monocarboxylic acids. In a preferred embodiment of the present invention the monomers M2 are selected from the C1-C12-alkyl esters of acrylic acid and C1-C12-alkyl esters of methacrylic acid, especially methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate and 2-ethylhexyl acrylate. Based on the overall monomer amount, the monomers M2 make up preferably at least 80% by weight and in particular at least 90% by weight. The remainder of the abovementioned comonomers (referred to below as comonomers Mxe2x80x2) are generally used in amounts  less than 50% by weight, preferably  less than 20% by weight and, in particular,  less than 10% by weight, based on the overall amount of the monomers M. A preferred embodiment of this invention relates to copolymers P which incorporate none of the abovementioned comonomers Mxe2x80x2.
In a preferred embodiment of the invention the copolymers P comprise copolymerized monomers M3 which have urea groups, examples being N-vinyl- and N-allylurea and derivatives of imidazolidin-2-one, such as N-vinyl- and N-allylimidazolidin-2-one, N-vinyloxyethylimidazolidin-2-one, N-(2-(meth)acrylamidoethyl) imidazolidin-2-one, N-(2-(meth)acryloxyethyl)-imidazolidin-2-one, N-[2-((meth)acryloxyacetamido)ethyl)-imidazolidin-2-one etc. The monomers M3 are preferably used in amounts of from 0.1 to 10% by weight, in particular from 0.5 to 5% by weight, based on the overall weight of the copolymer P. The monomers M3 improve the wet adhesion of the coatings obtainable from the formulations of the invention, i.e., the adhesion of the coating in the wet or swollen state.
The copolymers P can also include in copolymerized form monomers comprising siloxane groups (monomers M4), examples being vinyltrialkoxysilanes, such as vinyltrimethoxysilane, alkylvinyl-dialkoxysilanes or (meth)acryloxyalkyltrialkoxysilanes, such as (meth)acryloxyethyltrimethoxysilane, or (meth)acryloxypropyl-trimethoxysilane. The monomers M4 can be used in amounts of up to 1% by weight, preferably from 0.05 to 0.5% by weight, based on the overall monomer amount.
In addition, the copolymer P may also include in copolymerized form neutral or nonionic monomers M5 whose homopolymers feature increased solubility in or swellability in water. These monomers are preferably copolymerized in amounts of  less than 5% by weight and preferably  less than 2% by weight, based on the overall weight of the copolymer P. Monomers of this kind enhance the stability of the polymer dispersions. Typical monomers M5 are the amides, the N-alkylolamides or the hydroxyalkyl esters of the abovementioned carboxylic acids, such as acrylamide, methacrylamide, N-methylol-acrylamide, N-methylolmethacrylamide, 2-hydroxyethylacrylamide, 2-hydroxyethylmethacrylamide, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate.
In preparing the copolymers P it is also possible to employ bifunctional monomers M6. These are copolymerized if desired in minor amounts, generally from 0.1 to 5% by weight and, in particular, not more than 1% by weight, based on the overall monomer amount. Monomers M6 are preferably monomers having two nonconjugated ethylenically unsaturated bonds, examples being the diesters of dihydric alcohols with xcex1,xcex2-monoethylenically unsaturated C3-C8 carboxylic acids, such as glycol bisacrylate, or esters of xcex1,xcex2-unsaturated carboxylic acids with alkenols, such as bicyclodecenyl (meth)acrylate. Preferred polymers P contain no copolymerized monomers M6.
The character of the formulations of the invention is also dependent on the glass transition temperature (DSC, midpoint temperature, ASTM D 3418-82) of the copolymer P. If the glass transition temperature is too low, the coating is not very strong and tears when subjected to a mechanical load. If it is too high, the polymer no longer forms a film and the coating, consequently, is of reduced wet abrasion resistance. The glass transition temperature of the copolymers P in question is therefore below 50xc2x0 C. and preferably below 40xc2x0 C., in particular below 30xc2x0 C. In general, however, it is above xe2x88x9210xc2x0 C. It proves useful in this context to estimate the glass transition temperature. Tg of the dispersed polymer. According to Fox (T. G. Fox, Bull. Am. Phys.
Soc. (Ser. II) 1, [1956]123 and Ullmanns Enzyklopxc3xa4die der technischen Chemie, Weinheim (1980), p. 17, 18) the glass transition temperature of copolymers at high molar masses is given in good approximation by       1          T      g        =                    X        1                    T        g        1              +                  X        2                    T        g        2              +          …      ⁢              xe2x80x83            ⁢                        X          n                          T          g          n                    
where X1, X2 . . . , Xn are the mass fractions of the monomers 1, 2, . . . , n and Tg1, Tg2, . . . , Tgn the glass transition temperatures of the homopolymers of 1, 2, . . . , n, in kelvins. The latter are known, for example, from Ullmann""s Encyclopedia of Industrial Chemistry, VCH, Weinheim, Vol. A 21 (1992) p. 169 or from J. Brandrup, E. H. Immergut, Polymer Handbook 3rd ed., J. Wiley, New York 1989.
From what has been said above it is clear that the glass transition temperature of the copolymer P can be adjusted both by choosing an appropriate principal monomer M2, having a glass transition temperature within the desired range, and by combining at least one monomer M2a having a high glass transition temperature with at least one monomer M2b having a low glass transition temperature, the latter procedure being preferred.
In a preferred embodiment of the present invention the monomers M making up the copolymer P include at least one monomer M2a whose homopolymer, for the limiting case of a very high (infinite) molecular mass, has a glass transition temperature Tg greater than 30xc2x0 C. and at least one monomer M2b, whose homopolymer has a glass transition temperature Tg less than 20xc2x0 C. Examples of monomers M2a suitable for this purpose are styrene, xcex1-methylstyrene, methyl methacrylate, ethyl methacrylate, n- and iso-propyl methacrylate, n-, iso- and tert-butyl methacrylate, tert-butyl acrylate and vinyl acetate, and also acrylonitrile and methacrylonitrile, the two nitriles preferably accounting for not more than 30% by weight of the monomers M2a. Examples of monomers M2b suitable for this purpose are the C1-C12-alkyl acrylates, butadiene, vinyl versatates, and especially ethyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate. Particular preference is given to monomer combinations M2a/M2b which comprise styrene and/or methyl methacrylate and also n-butyl acrylate with or without 2-ethylhexyl acrylate.
In one particularly preferred embodiment of the present invention the copolymer P is constructed from:
i) from 20 to 80% by weight, preferably from 35 to 70% by weight, of monomers M2a, especially styrene and/or methyl methacrylate, specifically methyl methacrylate as sole monomer M2a,
ii) from 20 to 79.7% by weight, preferably from 30 to 65% by weight, of monomers M2b, especially n-butyl acrylate and/or ethylhexyl acrylate,
iii)from 0.1 to 1.5% by weight, preferably from 0.2 to 1.2% by weight, especially from 0.3 to 1.0% by weight and, with particular preference, from 0.5 to 0.8% by weight of itaconic acid,
iv) from 0.2 to 5% by weight, preferably from 0.5 to 3% by weight of monomers M3 having at least one urea group, especially an ethylenically unsaturated derivative of imidazolidin-2-one,
where the proportions by weight of the monomers M1, M2a, M2b and M3 add up to 100% by weight. Such copolymers P are frequently employed in formulations of the invention comprising solvents.
In another preferred embodiment of the present invention the copolymer P is constructed from:
i) from 20 to 69.7% by weight, preferably from 30 to 60% by weight, of monomers M2a, especially styrene and/or methyl methacrylate, specifically styrene as sole monomer M2a,
ii) from 30 to 80% by weight, preferably from 40 to 70% by weight, of monomers M2b, especially n-butyl acrylate and/or ethylhexyl acrylate,
iii) from 0.2 to 1% by weight, preferably from 0.4 to 0.9% by weight, especially from 0.5 to 0.8% by weight of itaconic acid,
iv) from 0.1 to 3% by weight, in particular from 0.2 to 2% by weight, of monomers M5, especially acrylamide and/or methacrylamide,
where the proportions by weight of the monomers M1, M2a, M2b and M5b add up to 100% by weight. Such copolymers P are frequently employed in formulations of the invention that are solvent-free.
The copolymers P of the two preferred embodiments can of course be modified with siloxane groups, by means, for example, of copolymerized monomers M4 (see above) or by using regulators containing siloxane groups, examples being mercaptoalkyltri-alkoxysilanes such as mercaptopropyltrimethoxysilane.
It has additionally proven advantageous if the polymer particles in the binder polymer dispersion have a ponderal median polymer particle diameter in the range from 50 to 1000 nm (determined by means of an ultracentrifuge or by photon correlation spectro-scopy; regarding the determination of particle size by means of an ultra-centrifuge see, for example, W. Mxc3xa4chtle, Makromolekulare Chemie 185, (1984) 1025-1039 and W. Mxc3xa4chtle, Angew. Makromolekulare Chemie 162 (1988) 35-42). In the case of binder dispersions with high solids contents, such as  greater than 50% by weight, based on the overall weight of the binder dispersion, it is advantageous on grounds of viscosity for the ponderal median diameter of the polymer particles in the dispersion to be xe2x89xa7250 nm. The median particle diameter will generally not exceed 1000 nm and preferably will not exceed 600 nm.
The aqueous polymer dispersions employed in accordance with the invention are preferably prepared by free-radical aqueous emulsion polymerization of the abovementioned monomers in the presence of at least one free-radical polymerization initiator and, if desired, of a surface-active substance.
Suitable free-radical polymerization initiators are all those capable of triggering a free-radical aqueous emulsion polymerization reaction. They can be peroxides, for example, alkali metal peroxodisulfates, or azo compounds. As polymerization initiators it is common to use redox initiators, which are composed of at least one organic reducing agent and at least one peroxide and/or hydroperoxide, examples being tert-butyl hydroperoxide with sulfur compounds, such as the sodium salt of hydroxymethanesulfinic acid, sodium sulfite, sodium disulfite, sodium thiosulfate or acetone bisulfite adduct, or hydrogen peroxide with ascorbic acid. Use is also made of combined systems which comprise a small amount of a metal compound which is soluble in the polymerization medium and whose metal component can exist in a plurality of valence states, an example of such a system being ascorbic acid/iron(II) sulfate/hydrogen peroxide, where the ascorbic acid is frequently replaced by the sodium salt of hydroxymethanesulfinic acid, acetone bisulfite adduct, sodium sulfite, sodium hydrogen sulfite or sodium bisulfite, and the hydrogen peroxide by organic peroxides, such as tert-butyl hydroperoxide, or alkali metal peroxodisulfates and/or ammonium peroxodisulfate. Initiators which are likewise preferred are peroxodisulfates, such as sodium peroxodisulfate. The amount of the free-radical initiator system that is employed, based on the overall amount of monomers to be polymerized, is preferably from 0.1 to 2% by weight.
Surface-active substances suitable for conducting the emulsion polymerization are the emulsifiers and protective colloids commonly employed for this purpose. The surface-active substances are normally employed in amounts of up to 10% by weight, preferably from 0.5 to 5% by weight and, in particular, from 1 to 4% by weight, based on the monomers to be polymerized.
Examples of suitable protective colloids are polyvinyl alcohols, starch derivatives and cellulose derivatives, or vinylpyrrolidone copolymers. An exhaustive description of further suitable protective colloids is given in Houben-Weyl, Methoden der organischen Chemie, Volume XIV/1, Makromolekulare Stoffe [Macromolecular substances], Georg-Thieme-Verlag, Stuttgart 1961, pp. 411-420.
As surface-active substances it is preferred to employ exclusively emulsifiers, whose relative molecular weights, unlike those of the protective colloids, are usually below 2000. They can be anionic or nonionic in nature. The anionic emulsifiers include alkali metal salts and ammonium salts of alkyl sulfates (alkyl: C8-C12), of sulfuric monoesters with ethoxylated alkanols (EO units: 2 to 50, alkyl: C12 to C18) and with ethoxylated alkylphenols (EO units: 3 to 50, alkyl: C4-C9), of alkylsulfonic acids (alkyl: C12-C18) and of alkylarylsulfonic acids (alkyl: C9 to C18), and also compounds of the general formula I, 
where R1 and R2 are hydrogen or C4-C24-alkyl, preferably C8-C16-alkyl, but are not both hydrogen and X and Y can be alkali metal ions and/or ammonium ions. Use is frequently made of technical-grade mixtures which have a proportion of from 50 to 90% by weight of the monoalkylated product, an example being Dowfax(copyright) 2A1 (R1=C12-alkyl; DOW CHEMICAL). The compounds I are widely known, from U.S. Pat. No. 4,269,749, for example, and are obtainable commercially.
Suitable nonionic emulsifiers are araliphatic or aliphatic nonionic emulsifiers, examples being ethoxylated mono-, di- and trialkylphenols (EO units: 3 to 50, alkyl: C4-C9), ethoxylates of long-chain alcohols (EO units: 3 to 50, alkyl: C8-C36), and polyethylene oxide/polypropylene oxide block copolymers. Preference is given to ethoxylates of long-chain alkanols (alkyl: C10-C22, average degree of ethoxylation: 3 to 50) and, of these, particular preference to those based on naturally occurring alcohols or on oxo alcohols having a linear or branched C12-C18-alkyl radical and a degree of ethoxylation of from 8 to 50. Preference is given to anionic emulsifiers or to combinations of at least one anionic and one nonionic emulsifier.
Further suitable emulsifiers are given in Houben-Weyl, op. cit. pp. 192-208.
The molecular weight of the copolymers P can be adjusted by adding small amounts, generally up to 2% by weight based on the monomers to be polymerized, of one or more molecular weight regulators, examples being organic thiocompounds, silanes, allyl alcohols, and aldehydes.
The emulsion polymerization can be conducted either continuously or by the batch procedure, preferably by a semicontinuous process. In semicontinuous processes the major amountxe2x80x94that is, at least 70%, preferably at least 90% of the monomers to be polymerizedxe2x80x94is supplied continuously, including by a staged or gradient procedure, to the polymerization batch. This procedure is also referred to as the monomer feed process. It has been found advantageous in this context for the major amount of the itaconic acidxe2x80x94that is, at least 50%, preferably at least 80%, in particular at least 90% and, with very particular preference, all of the itaconic acid to be supplied to the polymerization reaction by way of the monomer feed; in other words, no more than 50% of the itaconic acid and, with very particular preference, no itaconic acid is included in the initial charge to the polymerization vessel before the polymerization is begun. By monomer feeds are meant liquid monomer mixtures, monomer solutions or, in particular, aqueous monomer emulsions.
In addition to the seed-free preparation method it is also possible, in order to establish a defined polymer particle size, to conduct the emulsion polymerization by the seed latex process or in the presence of a seed latex prepared in situ. Processes for this purpose are known and can be found in the prior art (see EP-B 40419, EP-A-614 922, EP-A-567 812 and literature cited therein and also Encyclopedia of Polymer Science and Technologyxe2x80x2, Vol. 5, John Wiley and Sons Inc., New York 1966, p. 847).
The polymerization is preferably conducted in the presence of from 0.01 to 3% by weight and, in particular, from 0.02 to 1.5% by weight of a seed latex (solids content of the seed latex, based on overall monomer amount), preferably with a seed latex included in the initial charge (initial charge seed).
The preparation of the aqueous dispersions of the copolymers P can also be carried out by what is known as staged polymerization. This means a procedure in a 1st stage of which the monomers of the 1st stage are polymerized by free-radical aqueous emulsion polymerization, preferably in the presence of a seed latex, after which the monomers of the 2nd stage are polymerized in the aqueous dispersion of the resultant 1st-stage polymer. This may be followed by further polymerization stages. In such a procedure, the monomer mixtures of the 1st stage and of the 2nd stage differ in the nature of the monomers and/or in the relative proportions of the monomers. The nature of the monomers to be polymerized in the 1st and 2nd stages is preferably the same. Where the monomers M include both a monomer M2a and a monomer M2b, the monomer mixtures of the 1st stage differ from those of the 2nd stage by the proportion M2a/M2b. In particular, the proportion M2a/M2b in the 1st stage is greater than the proportion M2a/M2b in the 2nd stage. The proportion of the monomers of the 1st stage to the monomers of the 2nd stage lies preferably within the range from 1:10 to 10:1 and, in particular, in the range from 1:5 to 5:1. Staged polymerization achieves the polymerization of the monomers of the 2nd stage (and, where appropriate, of subsequent stages) onto the polymer particles of the 1st stage.
The pressure and temperature of polymerization are of minor importance. It is normal to operate at temperatures of between room temperature and 120xc2x0 C., preferably at temperatures from 40 to 95xc2x0 C. and, with particular preference, between 50 and 90xc2x0 C.
Following the polymerization reaction proper, it may be necessary to render the aqueous polymer dispersions of the invention substantially free from odoriferous substances, such as residual monomers and other volatile organic constituents. This can be done physically in a manner known per se, by distillative removal (especially by steam distillation), or by stripping with an inert gas. The residual monomer content can also be lowered chemically by means of free-radical postpolymerization, especially under the action of redox initiator systems, as are set out, for example, in DE-A 44 35 423. Postpolymerization is preferably conducted with a redox initiator system comprising at least one organic peroxide and one organic sulfite.
The dispersions of the copolymer P are preferably adjusted to a pH in the range from 6 to 10 before being used in the formulations of the invention, preferably by adding a nonvolatile base, examples being alkali metal hydroxides, alkaline earth metal hydroxides or nonvolatile amines.
By the method of emulsion polymerization it is possible in principle to obtain dispersions having solids contents of up to about 80% by weight (polymer content based on the overall weight of the dispersion). For practical reasons it is generally preferred to use polymer dispersions having solids contents in the range from 40 to 70% by weight for the formulations of the invention. Particular preference is given to dispersions having polymer contents of about 50% by weight. Dispersions having lower solids contents are of course suitable in principle for use for the formulations of the invention.
In accordance with the invention the copolymers P comprising itaconic acid are employed in the form of their aqueous polymer dispersions as binders in pigmented formulations that are used to coat substrates. Examples of what are meant by such formulations include polymer dispersion plasters, tile adhesives, paints and varnishes, and sealants or sealing compounds, especially for porous components.
A preferred embodiment of the present invention relates to formulations in the form of emulsion paints.
The formulations of the invention, preferably emulsion paints, generally contain from 30 to 75% by weight and, preferably, from 40 to 65% by weight, of nonvolatile constituents. By these are meant all those constituents of the formulation except for water, but at least the total amount of binder, extender, pigment, solvents of low volatility (boiling point above 220xc2x0 C.), such as plasticizers, and polymeric auxiliaries. Of these, the amounts accounted for by each class of constituent are
from 3 to 90% by weight, preferably from 10 to 60% by weight, by solid binder constituents (=copolymer P),
ii from 5 to 85% by weight, preferably from 10 to 60% by weight, by at least one inorganic pigment,
iii from 0 to 85% by weight, preferably from 20 to 70% by weight, by inorganic fillers, and
iv from 0.1 to 40% by weight, preferably from 0.5 to 15% by weight, by customary auxiliaries.
The pvc of the formulations is generally above 10%, for example from 15 to 85%. In one preferred embodiment of the invention it is within the range from 15 to 25%. In another preferred embodiment of the invention the pvc is in the range from  greater than 40% to 60% by weight, e.g., at about 45% by weight. In a further preferred embodiment of the invention the pvc is  greater than 60%, preferably  greater than 70%, and can be up to 85%.
Typical pigments for the formulations of the invention, especially for emulsion paints, are, for example, titanium dioxide, preferably in the rutile form, barium sulfate, zinc oxide, zinc sulfide, basic lead carbonate, antimony trioxide, and lithopones (zinc sulfide+barium sulfate). However, the formulations may also comprise color pigments, examples being iron oxides, carbon black, graphite, luminescent pigments, zinc yellow, zinc green, ultramarine, manganese black, antimony black, manganese violet, Paris blue or Schweinfurt green. In addition to the inorganic pigments the formulations of the invention may also include organic color pigments, examples being sepia, gamboge, Cassel brown, toluidine red, para red, Hansa yellow, indigo, azo dyes, anthraquinonoid and indigoid dyes, and also dioxazine, quinacridone, phthalocyanine, isoindolinone and metal complex pigments.
Suitable fillers include, in principle, alumosilicates, such as feldspars, silicates, such as kaolin, talc, mica, magnesite, alkaline earth metal carbonates, such as calcium carbonate, in the form, for example, of calcite or chalk, magnesium carbonate, dolomite, alkaline earth metal sulfates, such as calcium sulfate, silicon dioxide, etc. The fillers can be employed as individual components. In practice, however, filler mixtures have proven especially suitable, such as calcium carbonate/kaolin and calcium carbonate/talc. Dispersion plasters may also include relatively coarse aggregates, such as sands or sandstone granules. In emulsion paints, of course, finely divided fillers are preferred.
To increase the hiding power and to save on the use of white pigments it is common in the preferred emulsion paints to employ finely divided fillers (extenders), examples being finely divided calcium carbonate or mixtures of different calcium carbonates having different particle sizes. To adjust the hiding power, the shade and the depth of color it is preferred to employ blends of color pigments and extenders.
The customary auxiliaries iv include wetting agents or dispersants, such as sodium, potassium or ammonium polyphosphates, alkali metal salts and ammonium salts of polyacrylic acids and of polymaleic acid, polyphosphonates, such as sodium 1-hydroxyethane-1,1-diphosphonate, and salts of naphthalenesulfonic acids, especially their sodium salts. The dispersants are generally employed in an amount of from 0.1 to 0.6% by weight based on the overall weight of the emulsion paint.
The auxiliaries iv may also include thickeners, examples being cellulose derivatives, such as methylcellulose, hydroxyethyl-cellulose and carboxymethylcellulose, and also casein, gum arabic, tragacanth gum, starch, sodium alginate, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylates, water-soluble copolymers based on acrylic and methacrylic acid, such as acrylic acid-acrylamide and methacrylic acid-acrylate copolymers, and what are known as associative thickeners, examples being styrene-maleic anhydride polymers or, preferably, hydrophobically modified polyetherurethanes, as are described, for example, by N. Chen et al. in J. Coatings Techn. Vol 69, No. 867, 1997, p. 73 and by R. D. Hester et al. in J. Coatings Technology, Vol. 69, No. 864, 1997, 109, the content of which is hereby incorporated in its entirety by reference.
Examples of hydrophobically modified polyetherurethanes are polymers of the general formula II 
where Rf is a hydrophobic radical, preferably a linear or branched alkyl of 10 to 20 carbon atoms, Et is 1,2-ethylene, Sp is C2-C10-alkylene, cycloalkylene or arylene, k is from 50 to 1000 and l is from 1 to 10, the product kxc3x97l preferably being from 300 to 1000. The dispersants and/or wetting agents are employed in general in an amount of from 0.1 to 0.6% by weight, based on the overall weight of the emulsion paint.
Inorganic thickeners, such as bentonites or hectorite, can also be used. Thickeners are generally used in amounts of from 0.1 to 3% by weight, preferably from 0.1 to 1% by weight, based on the overall weight of the aqueous formulation. In addition, the auxiliaries iv generally also include defoamers, preservatives or hydrophobicizing agents, biocides, fibers or other constituents.
In addition, in order to adjust the film-forming properties of the binder polymers, the coating compositions may also comprise what are known as film-forming consolidating agents (plasticizers), examples being ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, alkyl ethers and alkyl ether esters of glycols and polyglycols, e.g., diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether, hexylene glycol diacetate, propylene glycol monoethyl ether, monophenyl ether, monobutyl ether and monopropyl ether, dipropylene glycol monomethyl ether, and mono-n-butyl ether, tripropylene glycol mono-n-butyl ether, and the acetates of said monoalkyl ethers, such as butoxybutyl acetate, and also alkyl esters of aliphatic mono- and dicarboxylic acids, such as Texanol(copyright) from Eastman, or technical-grade mixtures of dibutyl esters of succinic, glutaric and adipic acid. Film-forming auxiliaries are customarily employed in amounts of from 0.1 to 20% by weight, based on the copolymer P present in the formulation, so that the formulation has a minimum film-forming temperature of  less than 15xc2x0 C. and preferably in the range from 0 to 10xc2x0 C.
A distinction is often made between solventborne and solventless paints. Solventborne paints are preferably employed for exterior applications and solventless paints preferably for interior applications. Typical solventborne paints include not only the abovementioned film-forming auxiliaries but also, for the same purpose, hydrocarbons and/or mixtures thereof, with or without aromatic constituents, such as white spirits in the boiling range from 140 to 210xc2x0 C. The copolymers P in solventborne formulations often have a glass transition temperature TG xe2x89xa75xc2x0 C. and, preferably, xe2x89xa630xc2x0 C. In solventless paints the glass transition temperature is preferably xe2x89xa610xc2x0 C.
Furthermore, the formulations employed in accordance with the invention may also include crosslinking additives. Additives of this kind can be aromatic ketones, such as alkyl phenyl ketones unsubstituted or with one or more substituents on the phenyl ring, or benzophenone and substituted benzophenones, as photoinitiators. Photoinitiators suitable for this purpose are known, for example, from DE-A-38 27 975 and EP-A-417 568. Other suitable crosslinking compounds are water-soluble compounds having at least two amino groups, examples being dihydrazides of aliphatic dicarboxylic acids in accordance with DE-A-39 01 073, if the copolymer P comprises carbonyl-containing monomers in copolymerized form.
The formulations of the invention are stable fluid systems which can be used to coat a large number of substrates. Accordingly, the present invention also provides a method of coating substrates. Examples of suitable substrates are wood, concrete, metal, glass, ceramics, plastic, plaster, wallpaper and coated, primed or weathered substrates. The formulation is applied to the target substrate in a manner dependent on the form of the formulation. Depending on the viscosity and pigment content of the formulation and on the substrate, application may take place by means of rolling, brushing, knife coating or spraying.
The coatings produced using the formulations of the invention are notable for high wet abrasion resistance and good adhesion under damp conditions, i.e., in the wet or swollen state. An improved wet abrasion resistancexe2x80x94in other words, an improved mechanical stability of the coatings toward abrasive influences in the damp statexe2x80x94is favorable for the weathering stability and wet cleaning stability of the coatings and therefore means that they can be washed. Moreover, the coatings are not tacky, and feature high blocking resistance.
The advantageous properties of the copolymer P as binder relative to prior art binder polymers, and especially its improved wet abrasion resistance, is equally in evidence in the case of pigmented formulations having a pvc of  less than 40% and in the case of formulations having a pvc of  greater than 40% or a pvc of  greater than 60%. The advantages of the invention become particularly evident if the formulations have a pvc of  greater than 40% and up to 85%, for example, a pvc of about 45% or a pvc of from 70 to 80%. Accordingly, the present invention also provides for the use of the copolymers P to improve the wet abrasion resistance of pigment-comprising formulations.